Apparatus for regenerating and smoothing data



Dec. 23, l947. H. K. wx-:lss 2,433,006

APPARATUS FOR REGENERATING AND SMOOTHING DATA Filed June 18, 1942 4 Sheets-Sheet l T Jy f" 7 :1u 1v; allory Dec. 23, 1947. H. K. WEISS v 2,433,006

APPARATUS FOR REGENERATING AND SMOOTHING DATA Filed June 18, 1942 4 Sheets-Sheet 2 H. K. WEISS Dec. 23, 1947.

APPARATUS FOR REGENERATING AND SMOOTHING DATA Filed June 18, 1942 4 Sheets-Sheet 3 wua/wto/t/ Herbert K WE'155 4j/ www H. K. WEISS Dec. 23, w47.

APPARATUS FOR REGENERATING AND SMOOTHING DATA Filed June 18, 1942 4 Sheets-Sheet 4 laudo 4 5. .c s 5 W @0MM vim-1 nm w/.E mm 2/ W W 6 t a P. .f E W Lu w. H 0o no 0 M 1% w mw ma M 2 2 nu 0 y Patented Dec. 23, 1947 UNITED STATES'PATENT OFFICE APPARATUS FOR REGENERATING AND SMOOTHING DATA (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention relates to apparatus for automatically regenerating and/or smoothing data received from a manually Operated source.

It is a principal object of the invention to provide power aided apparatus for tracking a mov* ing target wherein the application of power will be controlled from a manually actuable source in accordance with a mathematical constant functionally related to the distance of the target from the tracking station.

A further object of the invention is to provide power aided apparatus for tracking a moving target in rectilinear, unaccelerated motion in accordance with the azimuth rate of the target about the tracking station wherein the azimuth rate is established by means manually operable in accordance with a mathematical constant and a conjugately operable rate mechanism adapted to establish a rate proportional to the reciprocal of the square of the distance of the target from the tracking station, or a similar aiding ratio.

A still further object of the invention is to provide apparatus for tracking a moving target that will regenerate the data set thereinto and drive a tracking device in accordance therewith.

Another object of the invention is to provide apparatus for tracking a moving target that will automatically regenerate and smooth data obtained in manually tracking in the target.

The speciiic nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a horizontal projection showing elements of data employed in the operation of the apparatus of this invention.

Fig. 2 is a schematic view showing a regenerative azimuth tracking apparatus in accordance with this invention.

Fig. 3 is a schematic view showing a modication of the apparatus of Fig. 2.

Fig. 4 is a schematic view showing a combination regenerative azimuth tracking and smoothing apparatus in accordance with this invention.

Fig. 5 is a schematic view showing a modica tion of `the apparatus shown in Fig. 4.

Fig. 6 is a schematic View showing apparatus conforming with the invention suitable for 2 smoothing data obtained from an independently operable data transmitting unit.

Fig. '7 is a graph showing an alternate aiding ratio that may be employed with the azimuth regenerative tracking apparatus.

Fig. 8 is a view showing certain elements of data used in the apparatus shown in Fig. 9.

Fig. 9 is a schematic view of a range regeneration apparatus conforming with the present invention.

In Fig. 1, which is a diagrammatic plan view of the target path and its relation to tracking station Gr. it is assumed that the target moves in azimuth with rectilinear unaccelerated motion (or ground velocity of Sg) from right to left along the line T-T, the present position of the target being the point To. The symbols appearing in Fig. 1 are identied as follows:

ea=rate of angular travel of target in azimuth in radians per second;

Ao=the angle included between Rm and Ro;

Rm=the least horizontal range to the target path R0=the horizontal range to the present position To of the target; and

Sg=the ground velocity of the target,

it will be observed that:

S, eos A0 Aeoa--w---Ro but hence by substitution SgRn R02 therefore, the azimuth rate about tracking station G for a target at present position To in rectilinear unaccelerated motion is the constant SgRm divided by the square of the present horizontal range R02. With this relationship in mind it then becomes apparent that if an apparatus is driven at a rate proportional to the reciprocal of Rs2 multiplied by a constant proportional to SgRm that it will have an angular velocity proportional to that of the target and may be employed to keep any desired instrument or apparatus trained upon the target to thereby track the same as it traverses its course. To this end I have provided apparatus embodying mechanism operable to produce a rate proportional to l/Rn2 and also operable to set up and multiply .this rate by the multielL= plying constant SgRm in conformity with the above theory.

In Fig. 2 apparatus showing one embodiment of the invention is disclosed. This apparatus is particularly arranged for regenerative azimuth tracking and comprises an azimuth gear I8 adapted to be rotated about its axis for the purpose of orientation and thereafter relatively fixed in such oriented position. The remainder of the apparatus shown in Fig 2 is mounted upon any type of suitable support I I arranged to be rotated about the azimuth gear I by means of a worm gear I2, shaft I3, differential |4, shaft I and handwheel I 6.

A three-dimensional cam I1 translatable in the value SgRm and rotatable in the value Ro, designed to have a lift proportional to SgRm/R02 is mounted upon support Il through the medium of a shaft I 8 for translatory axial and rotational movement. Translatory movement of cani I1 is effected through a bracket I9 associated with the cam, a lead screw 20 interthreaded with the bracket in such manner that the bracket will be translated upon rotation of the screw, and a mechanical train for rotating the screw comprising bevel gears 2|, 22, shaft 23, and bevel gears 24, 25 organized to transmit rotation of shaft I5 to the screw 28. Cam I1 is rotatable by means of a gear 26 affixed to the cam and intermeshing gear 21 attached to a shaft 28 rotatably mounted upon the support II.

There is also mounted upon support |I a conventional variable speed drive or rate mechanism generally indicated at 29. The rate mechanism comprises the constant speed motor 30, disk 3| disposed in driven relation to the motor, cylinder 32, and ball carriage 33 interposed between the disk and cylinder with the balls 34 thereof so arranged as to be enabled to transmit motion from the disk to the cylinder. The ball carriage 33 is provided with a follower arm 35 normally maintained in contact with the surface of cam I1 and a shaft 36 connected With cylinder 32 serves as the input shaft to a torque amplifier 31 from the rate mechanism. An output shaft 38 interconnects the torque amplifier and differential I4.

In the operation of the apparatus shown in Fig. 2, assuming that the same has been positioned at the tracking station G and the azimuth gear I Il fixed, an operator will rotate shaft I5 by means of handwheel I6 to rotate the support about the gear I0 through gear I2 and thereby cause any suitable type of sighting instrumentality mounted upon the support to be trained upon a target in azimuth. If the target is moving, the operator will continue to rotate shaft I5 to keep the sighting instrumentality trained upon the target and in so doing will rotate shaft 23 through bevel gears 24, 25 to rotate lead screw 20 through the bevel gears 2|, 22. Clutch 23C is interposed in shaft 23 to prevent rotation of bevel gears 22-2I until such time as the sighting instrumentality has been trained upon the target and the actual operation of tracking the target commenced. It should be understood that the clutch 23C remains disconnected until the operator has been able to train the sighting instrumentalities upon the target and preferably has tracked it for a short trial period. When the operator is ready to introduce the tracking rate into the device, the clutch 23C is first closed so that the ensuing tracking of the target will be transmitted to the cam I1 and will move it translationally in accordance with the rate of handwheel turning. Rotation of lead screw 20 will translate the cam I1 upon shaft I8 from a position corresponding to its normal zero setting an amount proportional to the constant SgRm by reason of the design of the cam, which it will be recalled is translatable in the value SgRm and rotatable in the value R0 to have a lift equal to SgRm/R02. Simultaneously with the translation of cam I1, the cam will also be rotated by shaft 28 and gear 21, angularly driven from a director or range device of any conventional type in proportion to the value of R0, to rotate the cam to a corresponding R02 position from an initial zero position. When cam I1 has been translated to SgRm and rotated to R02 from its normal zero position the lift SgRm/Ro2 thereof will displace follower 35 and ball carriage 33 correspondingly, and the disk 3| driven at a constant speed by the constant speed motor 30 will rotate the cylinder 32 through the balls 34 at a rate proportional to SgRm/R02. As the drive from disk 3| to cylinder 32 through the balls 34 is a frictional drive the output shaft 3B secured to cylinder 32 is not adapted to drive heavy loads, consequently, this shaft serves as the input shaft to a torque amplifier 31 which greatly augments the deliverable torque of shaft 33 through the output shaft 38. Output shaft 38 is connected to differential I4 and may drive the support about gear I0 through shaft I3 and gear I2. After the operator has initially tracked the target With handwheel I6 and shaft I5 to set up the constant SgRm on the cam I1 and shaft 28 is rotated to maintain a. position conforming to R0 the apparatus will automatically maintain itself trained upon a target having rectilinear unaccelerated motion through the power drive comprising the motor 30, rate mechanism 29, shaft 36, torque ampliiier 31, shaft 38, differential I4, shaft I3, and gear I2. It should be observed that the shaft 28 is rotated at all times from the director so that the three-dimensional cam I1 is continuously being rotated in accordance with the changing present range R0 of the target as determined by the director. As the target approaches midpoint, at

. the least horizontal range Rm, the value of R0 decreases; beyond the Rm point, the value of R0 increases. The rotation of cam I1 in correspondence with R0 will cause ball cage 33 to assume a position corresponding to the reciprocal of the R02 value. The mechanism thus obviates the usual unsteady state of operation which tends to accompany the manual operation of handwheel I6, shaft I5, differential I4 and gear I2, by setting up a steady and smooth rate mathematically proportional to the angular travel rate of the target in precise relationship upon which to base calculations in determining the future position of the target. If the target being tracked is in accelerated motion. either positive or negative, adjustment of handwheel I6 will be all that is required to adjust the changing SgRm, which if properly executed, will not affect the steady state operation accomplished through the power drive. As long as the target is in accelerated motion adjustment of handwheel I6 will be necessary, but, as soon as the target resumes unaccelerated motion handwheel I5 need no longer be adjusted.

Instead of using an aiding ratio that will effect a. displacement of the ball carriage 33 that varies with the reciprocal of R02 as above, I have found that for a particular combination of design scale factors that the aiding ratio may vary as a, function of horizontal range in the manner shown in Fig. 7 and give good results.

A modification of the apparatus disclosed in Fig. 2 is shown in Fig. 3 wherein the threedimensional cam I1 of the former apparatus has been omitted. In this instance an azimuth gear I and support II arranged to be relatively rotated with respect to each other as by the gear I2, shaft I3, differential I4, shaft |5, and handwheel I6 are provided as in the case of the apparatus shown in Fig. 2.

A two-dimensional cam 39 having a lift proportional to l/Rc2 is mounted upon the support for rotation about its axis by the gears 40, 4I, and shaft 42, which latter shaft is rotatable in values proportional to R0 by the director or range device associated with the apparatus. As indicated in Fig. 3 a conventional rate mechanism generally indicated at 43 is mounted upon the support II and has the disk 44 thereof driven by a constant speed motor 45 while the ball carriage 46 is displaceable by the follower 41 arranged' to engage and follow the cam surface of cam 39. The cylinder 48 driven by the balls 49 of the rate mechanism has affixed thereto a shaft 50 which drives the disk 5I of a second rate mechanism generally indicated at 52. The ball carriage 53 of rate mechanism 52 is displaceable in proportion to values of constant SgRm by means of a rack 54, pinion 55, shaft 56, and intermeshing bevel gears 51, 58 attached to shafts 56, I5, respectively. Cylinder 59 of rate mechanism 52 will rotate at a rate proportional to SgRm/Ro2, since the disk 5I thereof is driven by the rate mechanism 43 at a rate proportional to l/Rc2 and the ball carriage 53 thereof is displaced from itsnormal position of zero displacement by shaft I5 a distance proportional to SgRm.

The output rate of rate mechanism 52 is delivered to a dierential 6| through a shaft 60 affixed to cylinder 59 and the differential actuates a position operating switch 63 through shaft 62. A reversible capacitor motor 64 matches the input to differential 6| from rate mechanism 52, since the input to differential 6I from mechanism 52 will change the setting of position switch 63 and thereby cause motor 64 to run in the correct direction to reestablish the setting of the switch through the motor shaft 65, bevel gears 56, 61, and shaft 68, which latter shaft will subtract the input of shaft 60 to the differential 6I therefrom to maintain the switch properly positioned.

It is apparent that the motor 64, in maintaining a match of the input to differential 6| from shaft 60 and rate mechanism 52 will rotate shaft 66 at a rate proportional to shaft 60 or proportional to SgRm/Ro2 and therethrough drive the support II about gear l0 through differential I4, shaft I3, and gear I2 at a corresponding rate to maintain any sighting instrumentalities mounted upon support II trained upon a target in rectilinear unaccelerated motion that is being tracked. As in the case of the apparatus shown in Fig. 2 adjustment of handwheel I6 will adjust the output rate from rate mechanism 52 to the rate of a target in accelerated motion.

It sometimes occurs that it is desirable to smooth the tracking irregularities that may arise in the operation of the apparatus of Fig. 2 under certain circumstances, and to also correct for lag in response to changes in tracking data before transmitting the same to another station. For these purposes I have provided the apparatus of Fig. 4 wherein parts corresponding to similar parts of the apparatus shown in Fig. 2 are identied by similar reference characters. In addition to those parts corresponding to similar parts of Fig. 2 there is provided a second variable speed drive or rate mechanism generally indicated at 10 arranged to have its disk 1I driven by the shaft 12 through bevel gears 13, 14 in turn driven by the constant speed motor 30. The ball carriage 15 is displaceable from its normal position of zero displacement by means of the rack 16, pinion 11, differential 18, shaft 19, bevel gears 80, 6I and shaft I5 in the manner shown in Fig. 4. Cylinder 82 of the rate mechanism 10 is also connected with differential 18 by shaft 83 and to a second differential 84 by shaft 85. The differential 84 in addition to being coupled with cylinder 82 is coupled with. shaft 38 through the shaft 86 and bevel gears 01, 88. As clearly shown in Fig. 4 the output of differential 84 is transmitted to the fine and coarse azimuth transmission motors 89 and 90, respectively, through the gears 9|, 92, shaft 93, gears 94, 95 and shaft 96. In this construction it may be observed that shaft 38 delivers a smooth azimuth output, and that such output is equal to the input on shaft I3 plus or minus any added SgRm/Rn2 input from shaft I5 in conjunction with modifying action through slide I9, cam I1, etc. If by operation of the handwheel I6, and regenerative response of the apparatus the system has been matched with the angular velocity of a target being tracked, a sudden change in azimuth will be compensated for by the operator moving shaft I5 by means of handwheel I6, but shaft 38 will respond to the change more slowly thus tending to smooth the output from shaft 38 which drives the support I I and data transmitters 89, 90. Thus it is apparent that in all cases, since the rate mechanism 10 does not respond instantly to rotation 0f shaft I5, it will smooth out irregularities occurring in the manipulation of shaft I5.

Fig. 5 discloses a modified form of the regenerative tracking and smoothing apparatus shown in Fig. 4 and in this view the elements common to the apparatus shown in Figs. 2 and 4 are idented by corresponding characters. The system shown in Fig. 4 has the limitation that when settled on the target the operators handwheel I6 will be displaced from its normal zero position thereby causing generated azimuth as represented by the rotations of shafts I3 and 93 to lag actual azimuth by the amount of displacement of the handwheel which must be compensated for by the lag correcting rate mechanism 10, etc., in Fig. 4 before transmission. In the instant apparatus greater flexibility of adjustment of shaft I5 is gained by interposing a second variable speed drive or rate mechanism generally indicated at 91 between the operators handwheel I5 and lead screw 20. The second rate mechanism 91 is arranged to have its disk 98 driven by the constant speed motor 30 which drives the disk 3| of the first rate mechanism 29 through the bevel gears 99, |00 and shaft IUI. The ball carriage I02 of the second rate mechanism is displaceable from its normal position of zero displacement by the rack |03 and pinion |04 affixed upon shaft 23 whereby displacement of the ball carriage |02 will be effected by the operator in turning the shaft I5 by means of the handwheel I6. Cylinder 05 of the second rate mechanism is connected to the differential |06 in such manner as to add its output to the adjustment of shaft 23 to position lead screw 20. `After the combined action of shafts 23 and variable speed drive 91 has axially adjusted cam |1 to the position necessary to cause the target to be automatically tracked, it is necessary, to maintain this position, to center ball cage |02 relatively to disc 98. This is done by reversing the operation of handwheel |6 to restore it and shafts |5 and 23 to initial or starting position. The output of shaft 38 is then a smoothed version of azimuth, with no lag for rectilinear target courses. Similar to the apparatus of Fig. 4 ne and` Coarse azimuth transmitters |01, |08, respectively, are driven by shaft 38 through the gears |09, ||0, shaft and gears ||2, ||3. By the return of the shaft 23 to its normal position of zero displacement, the azimuth output of shaft 38 is rendered smooth in character, as it is devoid of the irregularities of manipulation of handwheel I6. and contains no lag for rectilinear courses of a target after lead screw 20 has been properly positioned. Moreover, in the case of uniformly accelerated targets, or targets pursuing a circle course about the tracking station in such manner that the rate of change of Rm is constant, an operator in using this apparatus will be enabled to nd a nal setting for handwheel I6 after which tracking of the target is accomplished by the apparatus automatically.

In Fig. 6 apparatus for smoothing azimuth data coming from an available azimuth unit not provided with such refinement is shown. In this apparatus incoming azimuth data will be received by the azimuth receiver ||4 and matched in a conventional manner by a follow-up motor ||5 controlled by the position switch ||6 in turn controlled by the azimuth receiver. The motor ||5 rotates a shaft which acts through bevel gears ||8, ||9, and shaft |20 to drive the differential |2| which is connected by shaft |22 and gear |23 to the position switch ||6. A variable drive or rate mechanism generally indicated at |24 has the cylinder |25 thereof driven by shaft |26, bevel gears |21, |28, shaft |29, bevel gears |30, |3I, shaft |32, bevel gears |33, |34, and constant speed motor |35. The cylinder |25 of rate mechanism |24 drives the disk |36 thereof through the balls |31 mounted in ball carriage |38. The ball carriage |38 is displaceable by the follower 41, cam 39, gears 40, 4| and shaft 42 in proportion to R02 so that the disk |36 is driven at a rate proportional to 1/Ro2.

A second variable drive or rate mechanism generally indicated at |39 is arranged to have its disk |40 driven from the disk |36 of rate mechanism |24 by a shaft 4| interconnecting the two disks. The ball carriage |42 mounting the balls |43 is interposed between the disk |40 and cylinder |44 and is displaceable from its normal zero position of displacement by means of the rack bar |45, rack |46, and pinion |41 attached to shaft |1. The cylinder |44 is connected by bevel gears |48, |49, and shaft |50 with a differential |5|. Shaft |50 is further interconnected with differential |2| by the bevel gears |52 and |53.

As clearly shown in Fig. 6 a third rate mechanism indicated at |54 has the disk |55 thereof driven by the motor |35 and the cylinder |56 is driven from the disk through the ball carriage |51 and balls |58. The cylinder |56 is connected by a shaft |59 to a differential |60 which latter is also connected to shaft 1. A pinion |6| is connected with the output side of differential |60 and engages a rack |62 which upon movement will displace the ball carriage |51 from its position of zero displacement by means of the interconnecting rack bar |63. Shaft |59 is also intergeared with differential |5| through the bevel gears |64, |65 and shaft |66 and differential |5| 8 is connected to the smooth azimuth transmitter |61 by shaft |68.

By the arrangement thus described with respect to Fig. 6 it will be seen that variable speed drive |24 produces a rate proportional to l/Ro2 and transmits such rate to variable speed drive |39 which multiplies it by SgRm to match the azimuth being received by receiver |4. The output of variable speed drive |39 is transmitted to differential |5| as a smoothed azimuth and to this azimuth so transmitted is added the lag correction supplied by variable speed drive |54 through shaft |66 and the differential |5|. The output from differential |5| is a smoothed version of the azimuth received by receiver I4 corrected for lag and is transmitted to the azimuth transmitter |61 by shaft |68.

For the purpose of obtaining smooth range setin, especially to be used in connection with the azimuth regeneration apparatus previously described, there is shown in Fig. 9 one desirable form of such apparatus. By referring to Fig. 8 it may be seen that in the right triangle shown (in which Dm, least slant height, is constant) that:

D02=y2+Dm2 (1) Differentiating (1) with respect to time D0D0=yy 2) Diiferentiating (2) with respect to time UODO) =y2=s2 (where sis constant speed of target) which shows that the rate of change of the product of range D and range rate Do is constant for a target in rectilinear unaccelerated motion.

The range regeneration apparatus comprises a shaft |10 connected to a differential |1| and is manipulatable by a handwheel |12. A first variable speed or rate mechanism indicated at |13 is arranged to have the ball carriage |14 thereof displaced from its position of normal zero displacement by the rack bar |15, rack |16, pinion |11,

shaft |18, bevel gears |19, |80, shaft I8| and bevel gears |82, |83 through rotation of shaft |10. Disk |84 of rate mechanism |13 is driven by the constant speed motor |85 which also serves to drive the disk |81 of a second variable speed drive or rate mechanism |86, by means of the bevel gears |88, |89, shaft |90, bevel gears |9|, |92 and shaft |93. Cylinder |94 of rate mechanism |86 is arranged to drive the disk |96 of a third rate mechanism |95 through the bevel gears |91, |98 and shaft |99. The ball carriage 200 of rate mechanism |86 is displaceable from its position of zero displacement by a two-dimensional cam 20| and follower 202. The cam 20| is functionally equivalent to the cam 39 of Figs. 3 and 6 and is designed to have a lift proportional to l/Du when rotated in proportion to Do by the gears 203, 204, shaft 205, bevel gears 206, 291, shaft 208, bevel gears 209, 2|0 and shaft 2| connected to the differential |1|. As clearly shown, the cylinder 2|2 of rate mechanism |13 is connected by a shaft 2|3 with differential 2| 4, the latter being connected with pinion |11 and a shaft 2|5. A pinion 2|6 is aixed to shaft 2| 5 in intermeshing relation with a rack 2|1 connected to the ball carriage 2|9 by the rack bar 2|8 whereby movement of the carriage from its normal position of zero displacement will be effected upon rotation of shaft 2|5. The cylinder 220 of rate mechanism |95 is connected to differential |1| by shaft 22|.

In operation the operator will turn handwheel |12 which will turn shaft |10 and shaft 2|| through differential |1| to control the range set in device. The output from shaft 2| I is fed back to cam 20| which displaces the ball carriage 200 in inverse proportional relation to the generated slant range Do. The disk |81 of rate mechanism |86 is rotated at a constant speed by the motor |85 so that cylinder |94 will have an output rate inversely proportional to range D thereby driving disk |96 of rate mechanism accordingly. Movement of handwheel |12 also adjusts the ball carriage |111 of rate mechanism |13 and through diiferential 2 I4, shaft 2 i 5, pinion 2 6, rack 2 I1 and rack bar 218 likewise adjusts the ball carriage 2|9 of rate mechanism |95. If the target is in rectilinear unaccelerated motion, shaft 2 5 will turn at a constant rate and rate mechanism |13 will settle to this correct rate, after which the operator need no longer rotate handwheel |12. With the constant of the system properly chosen the rotation of shaft 2|5 will be proportional to the product of range and range rate which as above shown is known to change at a constant rate. It may be observed that rate mechanism |13 could be eliminated in which case the apparatus becomes simply an aided tracking apparatus with an aiding ratio that increases with range. If rate mechanism |13 is sufliciently sluggish the response characteristics of the apparatus as revealed to an operator will be similar to those of a good aided tracking apparatus.

In interpreting the claims, it will be understood that the target is assumed to be moving in a rectilinear path with unaccelerated or constant speed and that the term present range means the instantaneous range of the target from a point in fixed spatial relation to the apparatus. It will also be understood that, where variable speed drives or variable speed devices are included, each is assumed to have an input operated at constant speed, a speed-varying element, and an output or output element operated at a speed proportional to the adjustment or position of the speed-varying element. Within these broad limitations any well-known variable speed devices may be used.

Speaking generally, the system performs a double integration from a course constant in order to obtain slant range continuously. The operators handwheel sets the constant. Now differentials 2| fl and |1| could be dispensed with if the operator could initially set the correct value of the course constant, and if the tracking device were initially on target, and all portions of the mechanism were in their proper initial positions. This is, of course, impossible, and the relations between the components of the mechanism must be such that the operator always makes a consistent response to a tracking error which he observes (i. e., he always moves his handwheel in the same direction to correct for a lag, but in the opposite direction to correct for a lead) and moreover, that these operator corrections, applied irregularly according to the acuity and physiological reaction time of the operator must cause the tracking device to settle toward the proper set of conditions when the ranging device (ranging and tracking devices are here considered to mean the same instrumentality which measures slant range) will be on target and the operator may release his control, after which the device will generate range continuously and accurately as long as the target performs rectilinear unaccelerated flight. Briefly, not only must the device be capable of providing a correct solution, but it must approach this solution correctly from any initial set of erroneous settings which may occur.

Referring to Figure 9 for an elementary statement of the functions of the elements. It has been derived that if the target flies a straight line atconstant speed, the rate of change of the product of range rate by range itself will be constant. Since in regenerative tracking it is desired to give the operator a control which will come to rest after an initial tracking period, his handwheel will be designated as the element which is to represent this course constant (henceforth called Y=d/dt (Do,D0) for brevity). The mechanism must therefore so operate as to correctly generate range if Y is correctly set, and to force the operator to make the proper settings to derive Y if (as will always be true) Y is not correct initially.

First, a shaft turning an amount proportional to slant range itself is desired. This is shaft 2| Now this shaft can always be made to turn to slant range if the mechanism between it and the operator is reasonably responsive, for the operator may be thought of as turning his handwheel in any manner necessary to make the range finder driven from shaft 2|| read the correct range. Of course it will be necessary to make the operators functions not only reasonable but simple.

Having a shaft representing slant range, the slant range rate is desired. Variable speed drive |95, |96, 220, generates a rate which is additive to the operators adjustment as it appears on shaft |10. If the cylinder 220 turns at less than the proper rate (and the operator makes no adjustment) the range finder will lag. The operator will make a natural corrective movement of his handwheel |12 to catch up, and in addition to this correction going straight through to the range finder over shaft |10, differential |1| and shaft 2| it will pass by means of shaft I8|, |18 through differential 2|4 to advance the rate output of variable speed drive at 220. As long as the rate of cylinder 220 is deficient, this process of adjustment will continue. When the rate is right, the shaft 2| will be driven continuously and automatically at the right rate to maintain range contact and the operator will need to make no further corrections.

It ls known, however, that the range rate itself 1s not constant, and with only variable speed drive at 220 to assist, the operator would continually be making new adjustments to compensate for the change in range rate. Use of the constancy of the rate of the product of range and range rate is now introduced. The disc |96 of the rate generating variable speed drive is caused to rotate at a rate proportional to l/Do. In order to stay on target, cylinder 220 must still turn at the range rate Do. 4The only ball cage position which will permit this, however, is one which places the balls a distance proportional to DoDo from the center of the disc. Then the cylinder rate, when the device has settled on target is 150, the disc rate is again l/Do since the range finder is being maintained on target, and the ball cage displacement is DcDo.

But it has been shown that even DoD@ is not constantonly the rate of its product being invariant. Hence, without the assisting mechanism of variable speed drive 2|2, the operator would continuously be required to turn his handwheel to move the ball cage to supply the rate of change of I'DoDo. It is known, however, that this is a constant rate, hence an additional variable speed drive may be introduced to supply the rate.

Again, the manner of its introduction must be such that no diicult manipulation on the part of the operator is required.

Note, therefore, that when an adjustment of handwheel |12 is made, the component which moves shafts |18 and 2I5 to adjust ball cage |95 also adjusts ball cage |13, thus causing a rate to appear on shaft 2|5 in addition to the direct adjustment communicated to shaft 2I5 by the adjustment of handwheel |12.

There now follows this sequence of operations: The operator does whatever is necessary to his handwheel to get initial range contact and to maintain it. It is not immediately evident, but actually the mechanism allows him to make this adjustment conveniently. It is apparent that one result of an adjustment of handwheel |12 is an immediate and proportional movement of shaft 2| I, and therefore, an immediate adjustment in position of the range finder, so that the operator is immediately cognizant of the qualitative eifect of his correction. Since the quantitative effect also involves the two integration processes, these are not immediately apparent to the operator, but each integration process is modified in the same direction (by choice of sign of the gearing) as the basic handwheel adjustment. This condition is a requirement for stable operation of the device. Thus, if the device lags the target range, the operator turns his handwheel to catch up. This adjustment is at once apparent to the operator as stated above; hence, he does not tend to over-correct. The same adjustment, however, also immediately (by the component which passes directly through differential 2M) increases the rate of cylinder 220, thereby causing the device to have less tendency to lag the target after the adjustment, and the same adjustment by moving ball cage |13 increases the rate of cylinder 2I2, and hence, of ball cage |95 so that the rate of change of rate of cylinder 223 is increased, thus anticipating future increases in the targets range rate.

It is evident intuitively, and can be demonstrated mathematically by writing the differential equations of motion relating the integration processes, that any adjustment of handwheel |12 must make a correction of the position of ball cage |13 which is not too large with relation to the concomitant adjustments in position (through differential I1I) and in rate (at ball cage |95), or the acceleration of motion of ball cage |95 will be so great as to cause overshooting and hunting about the true target position.

Now, providing that the various gear ratios have been so chosen as to prevent the tendency of this device to overcorrect, it will be seen from the foregoing discussion that regardless of the initial position of any of the elements, the natural response of the operator in turning his handwheel to get on target, and thereafter to stay there, will be such as first to cause shaft 2II to move to a position proportional to slant range; second, to cause ball cage |95 to move to a position proportional to DnDo; and third, to move ball cage |13 to a position proportional to cl/dtL (DoDo) or Y. But Y is a constant, hence, with the mechanism and the range finder on target, and ball cage |13 at a position proportional to Y, the operators handwheel which is directly geared through shaft I8| and |18 to ball cage |13 is in a position which is also proportional to Y. Since Y is constantthe position of the operators handwheel is a constant.

Describing the process physically, the operator trains his sight on the target, then finds that his handwheel must be turned slower and slower (or smaller and smaller corrections) until he may release it, and his range finder will stay continually on target until the target maneuvers. Since the range being produced is the result of machine integration it will be smooth.

With regard to the shafts I3 and 92 of Figure 4, the whole instrument is considered as a tracking device supplying azimuth data by means of data transmitters 89 and 9D to a computer which may or may not be integral with the tracking head. Then the position of shaft 92 is a smoothed version of the position of shaft I3 in the following way: shaft 36 is the generated azimuth rate of the instrument. Now there will always be small tracking disturbances caused by the observer who will be continually trying to improve his control setting or adjusting it to conform to displacements of the airplane from straight flight caused by atmospheric irregularities. The integration process between the handwheel I6 and the shaft 36 tends to smooth out these irregularities in the rate, but the position component transmitted by shaft I5, differential I, and shaft I3 conveys the irregularities. Hence, it is not desirable to employ the position of shaft I3 as smooth azimuth since this would require the observer himself to ignore small irregular disturbance of the airplane rate from the generated rate. It is better to provide an additional mechanism which eliminates the necessity of discretion on the part of the operator and allows him to follow all airplane disturbances. This is the variable speed drive 10, the cylinders of which reproduce but sluggishly the position of shaft 19, so that disturbances of shaft 19 of short duration compared with the matching time of variable speed drive 1U will not be transmitted to drum 82. The addition of position of shaft S5 to position of shaft 8B at differential 84 then corresponds to the addition of position of shaft 38 to the position of shaft I5 at differential I4 with the exception that the position of shaft is an average of the successive positions of shaft I5 over an interval of time. Then shaft 92 corresponds in position to shaft I3 except that it does not reproduce the short time disturbances which may appear on shaft I3 by adjustments of the operator.

The apparatus of Figure 6 is intended to constitute an intermediate unit which might be located between a tracking device such as a radio locator, and a computing device. It might, however, be built integral with either. Azimuth tracking data which might be quite irregular as produced by errors of the tracking device are received and duplicated as shaft movement by Selsyn I I4 and motor I I5. The rest of the circuit operates on this received data to smooth it according to the known law by which azimuth rate must vary (i. e., SgRm/Ro2) and Selsyn transmitter |61 then transmits the smoothed and, therefore, improved data to the computing unit which performs the prediction and ballistic transformations.

Having now described what is regarded as the presently preferred embodiment of the apparatus, I claim:

1. In apparatus for tracking a moving target traversing the leg of a right triangle in accordance with the relation SgRm/Ro2, where Sg is the ground speed of the target; Rm is the least range or leg of the triangle adjoining the leg thereof being traversed by the targets, and Ro is the slant range or hypotenuse of the triangle,

a first shaft rotatable from an initial position in proportion to SgRm, a second shaft, a differential interconnecting said first and second shafts, a drive mechanism having a variable speed output drive, a three-dimensional cam translatable from an initial position in proportion to SgRm and rotatable in proportion to Ro, to thereby effect -a lift proportional to SgRm/Ro2, means interconnecting the first shaft and cam for translating the cam in scale relation, means for rotating the cam, a follower directly interposed between the cam and drive mechanism for regulating the output drive of the drive mechanism to a speed proportional to SgRm/Ro2, and means directly connecting the output drive of said drive mechanism with the third element of the differential in driving relation; whereby the second shaft may ultimately be power driven through said diiferential at a rate proportional to SgRm/Roz.

2. In apparatus for tracking a target moving along a supposedly rectilinear path, a three-dimensional cam adapted, when adjusted in a first dimension in accordance with present range of said target, and in a second dimension in accordance with a factor equal to the product of speed of said target and minimum distance of said path from a predetermined position, to elfect a resultant movement proportional to said factor divided by the square of said present range, manually operable means connected to move said cam in said second dimension, a rst variable speed drive having its speed-varying element controlled by said cam in accordance with said resultant movement, a second Variable speed drive, a first differential having one side connected to be actuated by said manually operable means, and its second and third sides in driving connection with the speed-varying element and output respectively, of said second variable speed drive, a second differential having rst and second sides connected to be driven by the outputs of said first and second variable speed drives, respectively, transmitter means connected to be driven by the third side of said second differential, a shaft, a third diiferential having its first, second and third sides connected in driving relation, respectively, with said manually operable means, the output of said first variable speed drive, and said shaft, and means driven by said shaft to track a target.

3. In an apparatus fo-r tracking a target supposedly moving in a rectilinear path, a threedimensional cam adapted, when moved in a first dimension in accordance with present range of said target, and in a second dimension in accordance with a factor equal to the product of speed of said target and minimum range of said path, to produce a third movement proportional to said factor divided by the square of said present range, means controlled by said cam and producing an output speed proportional to the time integral of said third movement, first, second, and third differentials, variable speed smoothing means including two sides of said rst differential and having an output connected to drive one side of said second differential, the second sides of said second and third differentials being driven by said rst named means in proportion to said output speed thereof, a single manually operable means connected to simultaneously move said cam in said second dimension, and to actuate the rst sides of said first and third differentials, means driven by the third side of said third differential producing an output for driving a tracking device, and telemetric transmission mea-ns connected to be driven by the third side of said second differential.

4. In an apparatus for tracking a target moving along an assumedly rectilinear path, a threedimensional cam adapted to be moved in one dimension proportional to present range of said target and in a second dimension proportional to a factor equal to the product of target speed and minimum range of said path from a point adiacent said apparatus, to thereby effect an output movement equal to said factor divided by the square of said present range, rst and second variable speed drives, each having an output and a speed-varying element, means moving said speedvarying element of said rst variable speed drive in response to said output movement of said cam, a first differential, a single manually operable means connected to actuate said cam in said second dimension and a rst side of said first differential, the second and third sides of said rst differential being connected, respectively, to the speed-varying element and output of said second variable speed drive, a second differential, means connecting the outputs of said variable speed drives to first and second sides, respectively, of said second differential, and telemetric transmission means connected to be driven by and in straight line proportion to the movement of the third side of said second differential.

5. An apparatus as in claim 4, a constant speed motor, an input for each of said variable speed drives, and a driving connection between each said input and said motor.

6. An apparatus for tracking a target moving along an assumedly rectilinear path comprising a manually operable shaft, a three-dimensional cam rotatable on an axis and adapted, when rotated proportional to present range of a target and translated along said axis proportional to a factor equal to the product of speed of said target and minimum range of said path, to produce a lift equal to said factor divided by the square of present range, a driving connection so translating said cam in response to operation of said shaft, a rst variable speed drive having a speedvarying member, means controlling said member by and in proportion to the lift of said cam, a second variable speed member, a first differential having its first side connected to be operated by said shaft and having its second and third sides connected respectively to the speed-varying member and output of said second variable speed drive, a second differential having first and second sides connected, respectively, with the outputs of said variable speed drives, and telemetric transmitter means connected to be driven by the third side of said second diiferential.

7. An apparatus for tracking a target, comprising a first differential, first and second shafts connected to respective sides of said differential, a three-dimensional cam rotatable about an axis in proportion to present range of said target and translatable along said axis in proportion to a factor equal to the product of target speed along a path and minimum range of said path, said cam being formed to effect a lift, when so rotated and translated, equal to said factor divided by the square of said present range, a driving connection translating said cam in response to rotation of said first shaft, means for rotating said cam, a first variable speed drive, a follower actuated by the lift of said cam and effective to vary the output of said rst variable speed drive, a second variable speed drive, second and third differentials, means operating the first side of said differential in response to rotation of said rst shaft, means connecting the speed control element and output of said second variable speed drive tothe second and third sides, respectively, of said second diierential, lmeans connecting the outputs of said variable speed drives to respective sides of said third differential, a connection driving the third side of said rst differential from the output of said rst variable speed drive, means driven by said second shaft for tracking a target, and telemetric transmission means connected to be driven by the third side of said third differential.

8. In a regenerative tracking apparatus for a tracking device, rst means adaptedto e1ie ct.afrst movement proportional to the instantaneous l said point, third means combining said rst and second movements to effect a resultant movement proportional to said product divided by the square of said instantaneous range,'fourth means controlled by said resultant movement to effect an output movement having a, rate proportional to said resultant movement, diierential means, connections driving first and second sides of said diiierential means from said second and said output movements, respectively, and a driving connection from the third side of said differential means to angularly move said tracking device.

9. In a regenerative apparatus for tracking a target proceeding along a rectilinear path at constant speed, iirst means adapted to be operated to produce a, first movement proportional to the instantaneous range of said target from said apparatus, second means manually operable to produce a second movement proportional to the product of the speed of said target and the minimum range of said path from said apparatus, third means responsive solely to said iirst and second movements to produce therefrom a resultant output movement having a rate proportional to said product divided by the square of said instantaneous range, said third means including a cam moved by said rst means to give a lift inversely proportional to the square of said instantaneous range, diiierential means, means 16 drivingly connecting said second and third means to respective sides of said differential means, and means operated by a third side of said diierential means to angularly move a tracking device in proportion to the algebraic sum of rst and said resultant output movements,

10. In a regenerative tracking apparatus for tracking a target proceeding along a rectilinear path at constant speed relatively to a point adjacent said apparatus, rst means movable in accordance with the instantaneous range of said target,y second means movable to produce a movement 'proportional to the product of the speed of said target and the minimum range of said path from said point, third means operated by and responsive solely to'the said movements of said first and'v second means to combine the same and produce an output movement having a rate proportional to said product divided by the square `of-said instantaneous range, differential means, connections driving rst and second sides of said differential means by" andv from said second means' and said third means, respectively, and -means actuatedbythe third side of said differential means to angularly move a tracking device.

` HERBERT K. WEISS.

Y REFERENCES CITED i The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,177,470 Barr etal Mar. 28, 1916 1,453,104 Gray Apr. Z4, 1923 1,831,595 Gray Nov. 10, 1931 1,974,864 Fletcher Sept. 25, 1934 2,066,499 Watson Jan. 5, 1937 2,071,424 Papello Feb. 23, 1937 2,105,985 Papello Jan. 18, 1938 2,206,875 Chafee et al, July 9, 1940 2,377,898 Myers June 12, 1945 2,378,910 Chafee et al June 26, 1945 2,385,952 Svoboda Oct. 2, 1945 FOREIGN PATENTS Number Country Date 371,517 Great Britain Apr. 28, 1932 

